PCA9557DGVR - 8-Bit I2C I/O Expander | Texas Instruments
MPN: PCA9557DGVR ✓ ActivePCA9557DGVR Overview
An I/O expander extends the number of digital input and output pins available to a host controller without adding a dedicated parallel-port bus. The I2C interface carries commands and data over two shared wires, while SMBus compatibility supports common embedded control architectures. This places the PCA9557 within the hierarchy of interface IC, bus expander, GPIO controller, and power-management-aware embedded peripheral.
The PCA9557 combines eight independently configurable I/O ports, an active-low reset input, and dedicated configuration registers. Its low standby-current capability, rated at 1 µA maximum in the manufacturer datasheet, makes it suitable for systems that spend significant time in a reduced-power state. The 2.3 V to 5.5 V operating range covers common low-voltage logic systems and 5 V peripheral boards.
The active-low RESET input allows a system controller to restore the power-on register state and initialize the I2C or SMBus state machine without removing power from the device. Configuration registers provide centralized control of the port behavior, while the eight ports can be individually programmed for input or output operation. The 400 kHz bus capability provides a practical balance between transfer throughput, wiring simplicity, and low system complexity.
Typical uses include industrial control panels, programmable LED indicators, key scanners, sensor and relay interfaces, and compact embedded control boards. The PCA9557 is especially useful when the primary microcontroller or application processor has too few GPIO pins for switches, indicators, interlocks, or remote digital I/O.
Design the PCB with short I2C traces, pull-up resistors on SDA and SCL, and a deliberate address assignment through the A0, A1, and A2 pins. Account for the active-low reset signal, validate output drive current for each connected load, and keep bus capacitance and voltage rise time within the limits stated in the manufacturer datasheet.
This page combines the manufacturer's functional description, exact ordering information, package details, interface characteristics, and application-oriented engineering guidance. It also distinguishes verified drop-in alternatives from devices that require footprint or function review, helping engineers shorten sourcing and design-in work.
Drop-in alternatives for PCA9557DGVR — same package, pin-to-pin compatible. Different-package parts requiring PCB rework are excluded.
Variants in this series
Same-series models that are drop-in compatible with PCA9557DGVR (same form factor and footprint) — differing in Configuration Registers, Operating Temperature, Package, Reset Input.
PCA9557PWG4
✅ Drop-In📋 Reference alternative (not in catalog)
PCA9557D
✅ Drop-InContact for price
View Datasheet →PCA9557PWRG4
✅ Drop-In📋 Reference alternative (not in catalog)
PCA9557DGVR Specifications
| Device Type | 8-bit I2C and SMBus low-power I/O expander |
| Number of I/O Ports | 8 ports |
| Operating Supply Voltage | 2.3 V to 5.5 V |
| I2C Bus Frequency | 400 kHz |
| SMBus Compatibility | Supported |
| Standby Current | 1 µA maximum |
| Reset Input | Active-low RESET input |
| Configuration Registers | Supported |
| Power-On Reset | Registers and I2C/SMBus state machine initialize on power-on |
| Operating Temperature | -40 °C to +85 °C |
| Package | 16-pin TVSOP |
| Pin Count | 16 pins |
| Mounting Type | Surface mount |
PCA9557DGVR Pin Configuration
| Pin 1 | RESET — Active-low reset input |
| Pin 2 | A0 — Hardware address input A0 |
| Pin 3 | A1 — Hardware address input A1 |
| Pin 4 | A2 — Hardware address input A2 |
| Pin 5 | P0 — Configurable I/O port P0 |
| Pin 6 | P1 — Configurable I/O port P1 |
| Pin 7 | P2 — Configurable I/O port P2 |
| Pin 8 | P3 — Configurable I/O port P3 |
| Pin 9 | GND — Ground connection |
| Pin 10 | P4 — Configurable I/O port P4 |
| Pin 11 | P5 — Configurable I/O port P5 |
| Pin 12 | P6 — Configurable I/O port P6 |
| Pin 13 | P7 — Configurable I/O port P7 |
| Pin 14 | SCL — Serial clock input |
| Pin 15 | SDA — Serial data input and output |
| Pin 16 | VCC — Power supply connection |
Typical Applications
PCA9557DGVR is suitable for 6 applications: Industrial Control Panels, LED Status and Signage Control, Sensor and Relay Interfaces, Battery-Powered Embedded Devices, Programmable Key Scanners, Communication and Network Equipment.
Industrial Control Panels
The PCA9557DGVR fits industrial control panels that need more digital points than the main controller provides. Its eight configurable ports can connect selector switches, status indicators, relay-control logic, or acknowledgment signals to an I2C bus operating as high as 400 kHz. The 2.3 V to 5.5 V operating range supports both low-voltage control logic and 5 V interface levels. The active-low reset input lets a supervisory controller restore a known port state after a bus timeout without cycling the panel supply.
Recommended
LED Status and Signage Control
The PCA9557DGVR can expand a controller into an eight-channel LED or sign-control interface while keeping the wiring on a compact two-wire bus. Individual ports can be configured for output operation, allowing the host to update indicator states through the I2C interface at speeds up to 400 kHz. Its low standby current, specified as 1 µA maximum in the Texas Instruments manufacturer datasheet, helps conserve power in intermittently illuminated systems. Confirm each port's sink and source limits against the LED driver configuration.
Recommended
Sensor and Relay Interfaces
The PCA9557DGVR is useful for connecting discrete sensors, interlocks, and relay-control inputs where the host lacks sufficient GPIO. Its eight quasi-bidirectional ports can be configured individually for input detection or output control, and the I2C/SMBus interface reduces the number of traces required on a compact control board. The 2.3 V to 5.5 V range accommodates common embedded rails, while the active-low RESET input provides a deterministic recovery mechanism after a controller or bus fault.
Recommended
Battery-Powered Embedded Devices
The PCA9557DGVR suits battery-powered embedded equipment that periodically wakes to read controls or update outputs. The manufacturer datasheet specifies a standby-current maximum of 1 µA, while the device retains eight configurable I/O ports and I2C/SMBus connectivity at up to 400 kHz. This combination supports low-duty-cycle designs that need more interface pins without adding a large parallel bus. Power-budget calculations should include host-controller wake-up current, pull-up resistors, and the loads connected to the eight ports.
Recommended
Programmable Key Scanners
The PCA9557DGVR can expand a host processor into a matrix-style key or switch input interface by assigning the eight ports to scanner rows and columns. Its I2C communication rate of up to 400 kHz is suitable for frequent polling and short command sequences, while the 2.3 V to 5.5 V supply range supports common logic voltages. The configuration registers provide centralized port setup, and the active-low reset path can return the scanner to its initial state after a firmware or communication fault.
Recommended
Communication and Network Equipment
The PCA9557DGVR can add discrete monitoring and control points to communication equipment without consuming a large share of the host processor's GPIO. It is suited to module-present indicators, fan or relay commands, alarm inputs, and hardware configuration straps where firmware must read and update the port state over I2C or SMBus. Its 400 kHz bus rate supports practical command throughput, and the 16-pin TVSOP package simplifies compact single-board designs. Use the manufacturer's timing and loading limits when calculating pull-up values for the deployed bus length.
Recommended
Recommended Products Summary
Engineering reference data for PCA9557DGVR — comparison, design guidance, and compliance information.
Selection Guide
Comparison with Alternatives
| Parameter | This Product | PCA9557PWG4 | PCA9557D | PCA9557PWRG4 |
|---|---|---|---|---|
| Package | 16-pin TVSOP | 16-pin SSOP | 16-pin SSOP | 16-pin SSOP |
| Brand | Texas Instruments | Texas Instruments | Texas Instruments | Texas Instruments |
| Device Type | 8-bit I2C and SMBus low-power I/O expander | 8-bit I2C and SMBus low-power I/O expander | 8-bit I2C and SMBus low-power I/O expander | 8-bit I2C and SMBus low-power I/O expander |
| Number of I/O Ports | 8 ports | 8 ports | 8 ports | 8 ports |
| Operating Supply Voltage | 2.3 V to 5.5 V | 2.3 V to 5.5 V | 2.3 V to 5.5 V | 2.3 V to 5.5 V |
| Maximum I2C Bus Frequency | 400 kHz | 400 kHz | 400 kHz | 400 kHz |
| Reset and Configuration Registers | Supported | Supported | Supported | Supported |
| Operating Temperature | -40 °C to +85 °C | -40 °C to +85 °C | -40 °C to +85 °C | -40 °C to +85 °C |
Key Differentiators
- Eight configurable I/O ports with dedicated configuration registers (vs PCA9557PWG4)
- Wide 2.3 V to 5.5 V operating range (vs PCA9557D)
- 400 kHz serial interface for control updates (vs PCA9557PWRG4)
Design Notes
Place SDA and SCL pull-up resistors close to the bus master or the electrically farthest connected device when bus segmentation requires distributed pull-ups. Select resistance using the bus voltage, capacitance, sink-current limit, and maximum rise-time requirement in the manufacturer datasheet. Keep the PCA9557 address inputs A0, A1, and A2 firmly tied to defined logic levels so the device receives a stable and unique address after reset.
Do not treat all eight ports as ordinary CMOS outputs without checking their drive and polarity behavior. The PCA9557 uses quasi-bidirectional I/O ports, and an output must be actively driven high or low as required by the interface design. Review the port-register semantics, power-on defaults, and electrical limits in the manufacturer datasheet before driving relays, LEDs, or devices that source current back into an output.
Route the PCA9557 supply from the same appropriate power domain as its directly connected logic unless level translation is provided. Keep the supply and ground planes continuous, place local bypassing close to VCC and GND, and verify that startup current does not disturb sensitive loads. The device's 1 µA maximum standby specification applies to the specified standby condition and should not be treated as the complete board-level sleep budget.
Respect the counter-clockwise pin numbering of the 16-pin TVSOP and verify pin 1 against the PCB footprint and package orientation mark. Keep the I2C traces away from noisy switching nodes and provide a continuous ground reference. Although the interface operates at a maximum 400 kHz, poor routing, excessive bus loading, or incorrectly valued pull-ups can still create timing violations on longer or multi-node boards.
Compliance Information
The manufacturer product and datasheet pages were identified, but explicit RoHS, REACH, AEC-Q100, lead-free, halogen-free, and conflict-minerals declarations were not included in the available product information.
